1. Field of the Invention
This invention relates to Group II metal carbonate overbased metal sulfonates and to lubricating oil additive concentrates and lubricating oil compositions containing them.
Lubricating oil compositions, particularly for use in internal combustion engines, have long performed many functions besides simply lubricating relatively moving parts. Modern-day, highly compounded lubricating oil compositions provide antiwear, antioxidant, extreme-pressure and antirust protection in addition to maintaining the cleanliness of the engine by detergency and dispersancy. Many lubricating oil additives are well known for accomplishing these functions.
2. Description of the Prior Art
Mixon et al, U.S. Pat. No. 2,367,468, teach the use in a lubricating oil of a composition prepared by reacting a hydrocarbon with chlorosulfonic acid and a sulfurizing agent followed by treatment with a neutralizing agent including the oxides, hydroxides, carbonates and bicarbonates of Group II metal salts. The treatment of isobutylene polymer with chlorosulfonic acid followed by treatment with alcoholic potassium hydroxide is specifically disclosed.
Wasley et al, U.S. Pat. No. 2,883,340, teach overbased polyolefin sulfonates for use as detergents in lubricating oil compositions. The polyolefin has a molecular weight from 10,000 to 50,000, and polyisobutylene or copolymers thereof are preferred.
British Pat. No. 1,246,545 discloses the use in a lubricating oil of a sulfonate prepared by reacting polyisobutylene with chlorosulfonic acid followed by treatment with lime to prepare the corresponding calcium polyisobutenyl sulfonate.
Methods for overbasing Group II metal petroleum sulfonates are taught in, for example, U.S. Pats. No. 3,027,325, 3,312,618, 3,422,013, 3,488,284, 3,492,231, 3,523,896 and 3,537,996.